Liquid quench, or as it is more commonly called `water quench`, extrusion has in the past traditionally been used for monofilament production, that is for filaments having a denier, after drawing, greater than 50. During the last ten years it has been realized that, with refinements, textile quality multi-filament yarns can be produced by water quench extrusion, that is multi-filament yarns in which the filaments are reasonably uniform and have, for example, a denier per filament of less than 35 after drawing. However, as attempts have been made to increase the rate of extrusion, and/or to decrease the denier of the filaments, problems have arisen.
One of these problems has been increased vortexing in the area where the molten filaments enter the quench water. This causes adjacent filaments to be brought together and, in their molten state, to adhere to each other to create fused filaments. Sometimes the vortexing is severe enough to cause the molten filaments to break, known as spin breaks.
Another of these problems that has arisen is a variation in the level of the quench water in the area where the molten filaments enter in. This may be caused by wave motions in the quench water, or by turbulence, or when extrusion is being started. Again, this may cause fused filaments or spin breaks; also, varying the distance between the spinnerette and the surface of the quench water, this distance being called the `hot stretch`, can adversely vary characteristics of the filaments.
U.S. Pat. No. 3,696,184 describes a baffle, or more commonly called a cage, arrangement which contributes towards reducing at least some of the above problems. A composite cage constituted of three concentric, foraminous, hollow cylinders closely surrounds the area where the molten filaments enter the quench bath. However, it has been stated that as production rates were increased, it was found that a cage which entirely surrounded the area at which the filaments entered the quench water could contribute to vortexing while reducing random turbulence.
U.S. Pat. No. 3,932,576 describes a further improvement to the arrangement in U.S. Pat. No. 3,696,184. The area in which the filaments enter the quench water is only partially surrounded by a half cage and in addition wetting agent is introduced at at least two symmetrical locations about the periphery of that area.
Although this latter arrangement has given satisfactory results, it has been found difficult to obtain steady running conditions when attempting to reduce the filaments to deniers, after drawing, of less than 25. Fused filaments became predominent and occasional spin breaks occurred. Also, separation problems occurred, that is a filament from one group of filaments would be displaced from that group and become included in an adjacent group. These problems became more acute when the number of filaments in a yarn were increased; for example, if instead of making a multifilament yarn having a drawn denier of 520 and 18 filaments, it was attempted to make a yarn having a drawn denier of 520 and 27 filaments. Not only is the denier per filament being reduced from 29 to 19, but also the number of filaments is being increased from 18 to 27.
It is observed that the finer the filaments, the greater is their surface to volume ratio which presumably increases the drag per denier through the quench water. It is also observed that the greater the number of filaments in a yarn, the closer together the filaments are extruded and the more readily they come in contact with each other while still molten.